Entraining a liquid into a fiber slurry to accelerate it prior to discharge from a flow path onto a forming wire

ABSTRACT

A slurry mixture of fibrous material and fluid is introduced into a predetermined flow path which leads to an exit aperture. A restricted opening preferably in the form of a slit is provided which communicates with the flow path at a predetermined location upstream from said exit aperture. An entraining fluid, such as clear or white water, is introduced through the slit and into the flow path whereupon the entraining fluid, due to a &#39;&#39;&#39;&#39;Coanda effect,&#39;&#39;&#39;&#39; attaches itself to a convexly-curved flow attachment surface positioned adjacent to said slit whereby said entraining fluid flows along said flow path in a direction toward said exit aperture at a velocity substantially greater than the flow velocity of the slurry upstream from the slit. The entraining fluid accelerates the slurry and causes same to exit from the exit aperture at a high rate of speed to the forming surface of a web-forming machine positioned adjacent to the exit aperture.

United States tt- 1191 Back et a1.

[ ENTRAINING A LIQUID INTO A FIBER I SLURRY TO ACCELERATE 1'11 PRIOR TODISCHARGE FROM A FLOW PATH ONTU A FORMING WIRE [22] Filed: Jan. 28,19741 [21] Appl. No.: 437,112

Related US. Application Data [63] Continuation of'Ser. No. 297,094, Oct.12,1972,

abandoned.

52 U.S. c1 162/216, 162/104, 162/129, 162 336, 162/338, 162/343,162/344,

51 1m. (:1 ..D21i1/02,D21fl/06 [58} Field of Search 162/216, 104, 129,336,

[56] References Cited UNITED STATES PATENTS 2,017,339 10/1935 Bryant eta1. 162/104 2,052,869 9/1936 Coanda... 28/114 X 2,615,374 10/1952 Malkin162/347 2,904,461 9/1959 Washburn et a1 162/344 X- 1451 Dec. 1111, 197 4Primary ExaminerS. Leon Bashore Assistant Examiner-Richard H. TushinAttorney, Agent, or Firm'Thomas R. Lampe [57] ABSTRACT A slurry mixtureof fibrous material and fluid is introduced into a predetermined flowpath which leads to I an exit aperture. A restricted opening preferablyin the form of a slit is provided which communicates with the flow pathat a predetermined location. upstream from said exit aperture. Anentraining fluid, such as clear or white water, is introduced throughthe slit and into the flow path whereupon the entraining fluid, due to aCoanda effect, attaches itself to a convexly-curved -flow attachmentsurface positioned adjacent to said slit whereby said entraining fluidflows along said flow path in a directiontoward said exit aperture at avelocity substantially greater than the flow velocity of the slurryupstream from the slit. The entrainingfluid accelerates the slurry andcauses same to exit from the exit aperture at a high rate of speed tothe forming surface of a web-forming machine posi tioned adjacent to theexit aperture.

24 Claims, 10 Drawing Figures PATENTEL k 3 853.59?)

NEW 18? 5 PMENIEL SEE I 0 I974 SHEET 4 0F 5 1 ENTRAINING A LIQUIDINTO AFIBER SLURRY TO ACCELERATE IT PRIOR TO DISCHARGE FROM A FLOW PATH ONTO AFORMING WIRE This is a continuation of application Ser. No. 297,094filed Oct. 12, 1972, now abandoned.

BACKGROUND OF THE INVENTION.

The present invention relates to an apparatus'and method for deliveringa fiber slurry to the forming surface of a web-forming machine, such asthe wire of a Fourdrinier-type papermaking machine.

In a typical web-forming machine, such as a papermaking machine, thefiber slurry, which is disposed in a headbox, is ejected from the exitslit of the headbox onto a Fourdrinier wire or other suitableweb-forming device by having energy transmitted directly to the fibersuspension or slurry itself. This is conventionally accomplished inexisting equipment by feeding the entire stream of fibrous slurrythrough a pump which exerts sufficient energy to expel the fibrousslurry at the desired velocity through the discharge orifice of theheadbox. Alternatively, the head of the slurry itself is utilized toforce the slurry out of the headbox discharge orifice. Such an approachobviously requires a headbox of great depth to maintain the exit speedof the slurry at a sufficiently high velocity to provide for properdelivery of the slurry as it exits from they headbox discharge orifice.Sometimes, the energy used to accelerate the fiber slurry is at leastpartially derived from a pressurized air cap above the slurry in theheadbox.

headboxes is the-nonuniform distribution of the energy applied to thesystem across the span of the discharge jet. Nonuniforrn distribution ofenergy ismanifested in several ways such as cross-machine velocitygradients, locally high or low velocities, transient disturbances,wakes, cross-flows and nonuniform turbulence scale. In turn, thesephenomena appear in the finished, dried, fibrous web as undesirablethick spots, thin areas, patterns or blemishes.

In addition to the nonuniform distribution of energy, the typicalheadbox also creates a situation of nonuniform distribution of fibers.Fibers in suspension tend to form flocs, clods, or agglomerations which,if not broken up in some manner, will likewise cause the finished,fibrous web to have undesirable local irregularities. In the case ofexisting web-forming machines, it has been necessary to employ rectifierrolls, baffles, tubes, converging plates or other physical means ofcontroling or acting upon the mass and energy distributions of theentire fibrous slurry in attempts to obtain uniform distribution ofenergy and fibers.

According to the present invention, many of these typical flow problemsare overcome so that the fiber suspension may be accelerated to thedesired uniform velocity and dispersion of fibers immediately 'prior todischarge to the forming wire or other forming surface of a web-formingmachine. This is accomplished by utilizing a phenomenon'known asthe-Coanda effect to indirectly accelerate the slurry. The Coanda effecthas been known for many years, as exemplified by US. Pat.

No. 2,052,869, issued ,to Henri Coanda'. Briefly, this phenomenon can bedescribed as the tendency'of a fluid, which emerges from a slit underpressure, to attach itself or cling to and follow a surface in the formof an extended lip of the slit, which recedes from the One major probleminherent in these typical existing 2 flow axis of the fluid as itemergesfrom the slit. This creates a zone of reduced pressure in the area ofthe slit so that any entrainable material which is in the zone willbecome entrained and flow with the fluid which has attached itself tothe extended lip.

SUMMARY According to the present invention, the Coanda effect has beenutilized as a direct means for introducing a high percentage of allenergy required to accelerate slurry fibers through a discharge orificeto a foaming surface. Specifically, energy is introduced into the slurrystream by forcing a fluid under pressure through a narrow slitcommunicating with. the slurry flow path and causing said fluid toattach itself to a convexlycurved fluid flow attachment surface adjacenttosaid slit whereby the entraining fluid, by virtue of the Coandaeffect, rapidly proceeds toward an exit aperture for the'slurry. Rapidflow of the entraining fluid after expulsion from the slit, induces flowof the slurry, causing same to be entrained and accelerated, and thecombined flows then mix and proceed toward the exit aperture. In otherwords, in contrast to conventional headbox arrangements wherein theslurry stream is pushed through the exit aperture, in apparatus con--structed in accordance with the present invention the slurry stream is,pulled through the exit aperture. Consequently, handling of long,fibrous materials is facilitated, without tangling and matting problemscustomarily associated with such materials. During-the interval from theslit to the exit aperture, the high, initial velocity and concentrationgradients between the two streams tend to level out resulting in arelatively uniform vertical slurry concentration and energydistributions at the point of discharge.

In practice, clear or white water under pressure may be utilized in thesystem of this invention as the entraining fluid. Because theentrainingfluid is a clear liquid, its energy content may be easily controled andmodulated, and many of the problems that usually attend attempts tomodulate and control velocity (or energy), such as nonuniformities inpulp slurry, are eliminated. Simple, inexpensive screens, and/or smalldiameter tubes whch are commonly used to smooth and control velocity andturbulence in clear fluids, may freely be used to achieve dessireddesired characteristics of entraining fluid expelled through the slit.In this way, the problems of shedding, plugging, etc., which areencountered when control of the entire process slurry stream isattempted, may be avoided.

Furthermore, the necessity of utilizing rectifier rolls is eliminateddue to the shear conditions imposed on 'the incoming, entrained fiberslurry. The velocity ratio between the entraining fluid andthe entrainedfiber slurry stream is in the order of at least ten in the region ofinitial mutual contact therebe'tween. The resultant highshear withcombined dilution breaks the flocs and creates a condition of uniformfiber dispersion as the entraining fluid and slurry mixture exittogether onto a web-forming surface.

The method and apparatus according to the present cessity for anypressure cap and/or direct pumping of the slurry. It also permits theuse of a low profile construction, and offers the ability to controlbasis weight of the web with minimum time delay. The invention has asits further aspect the provision of an improved method and apparatus fordelivering a fibrous slurry to a forming machine which is readilyadapted to a wide variety of slurry types and consistencies.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the present inventionare illustrated in the accompanying drawings in which:

FIG. 1 is a generally diagrammatic side view and partial section ofapparatus constructed in accordance with the principles of the presentinvention;

FIG. 2 is an enlarged cross-sectional view illustrating certainoperational details of the apparatus of FIG. 1.

FIG. 3 is a view taken along line 3- -3 of FIG, 1;

FIG. 4 is a view taken along line 44 of FIG. 1;

FIG. 5 is a vertical cross-sectional schematic view of a fragmentaryportion of an alternative embodiment of a machine constructed inaccordance with the teachings of the present invention;

FIG. 6 is an enlarged, vertical, cross-sectional schematic view of afragmentary portion of still another type of machine incorporating thepresent invention;

FIGS. 7, 8 and 9 are side elevational, sectional views showing selectedcomponents of still another alternative embodiment of a machineconstructed in accordance with the present invention, said componentsbeing illustrated in three separate, selected, operational GENERALDESCRIPTION Reffering now to FIGS. 1, 3 and 4, the apparatus constructedin accordance with the teachings of the present invention is indicatedgenerally by means of reference numeral 10'. Apparatus 10 includes abottom wall 12, end walls 14 and 16, and side walls 18 and 20. The wallsmay be constructed of any suitable material such as reinforced plasticor stainless steel and are secured together in any desired manner toprovide a generally box-like configuration. Disposed within the wallsare three segmented separate baffles 21, 23 and 36. Lower baffle 21 hasa top contour defined by the surface 22. Baffle 23 has a flow surface 24and is pinned and capable of rotation about its mounting pin -25 topermit minor adjustments of the flow channel defined between surfaces 22and 24. Baffle 36, having a flow surface 34, operatessimilarly to 23,and can be selectively moved about its mounting pin 27 to adjust theclearance between surfaces 34 and 22. Pins 25 and 27 extend between sidewalls 18 and and are mounted thereon in any suitable manner. Baffles 21,23 and 36 may be constructed of any suitable material such as plastic.With particular reference to FIG. 3, aplurality of divider panels 28extend lengthwise between the confines of side walls 18 and 20, therebydividing the apparatus 10 are adapted to maintain a constant head inreservoir 50 walls are separate segments or slices of baffles 21, 23

and 36, the respective contoured surfaces 22 24 and 34 of which form ineach chamber 30 a flow passage 100 (FIG. 1 The segments of baffles 21,23 and 36 are of a size to fit snugly against panels 28, therebypermitting easy adjustment of these baffles to vary the configuration ofthe flow passage. If desired, the baffles may be mounted for totalremoval from the rest of the apparatus.

A plurality of flexible slurry-supply conduits communicate with theinterior of each chamber 30 through apertures formed in end wall 16. Theslurry-supply conduits 40 are attached to the end wall 16 by suitablecoupling elements 42. The other ends of slurry-supply conduits 40 areconnected through valves 46 to the interior of head control box orreservoir 50. Reservoir 50 may be selectively moved up or down through asuitable mechanism (not shown) with respect to its supporting wall 52.Reservoir 50 is adapted to supply fiber slurry to apparatus 10 in amanner that will be described in greater detail below. A plurality ofsupply tubes 54 lead to the interior of reservoir 50 as shown. The otherends of the supply tubes are connected to a main fiber slurry stockreservoir (not shown) whereby reservoir 50 is continuously supplied fromthe main stock reservoir. One or more overflow lines 56 may be providedwhich and allow the overflow to return to the main stock reservoir. Therate of discharge from head control box or reservoir 50 may be controledby adjustment of valves 46 and/or by raising or lowering same withrespect to its supportingwall 52. v

Referring now to FIGS. 1, 2 and 4, apparatus 10 includes at the forwardor downstreamend thereof (the left-hand side of the apparatusas viewedin FIGS. 1 and 2) a mechanism utilizing the Coanda effect which inducesflow in the fiber slurry introduced in apparatus 10 and causes same toexit onto a web-forming surface such as a Fourdn'nier wire 58 which isconventionally joumaled on a breast roll 60 to receive the fiber slurryexiting from apparatus 10 in a manner to be described.

Depending from the downstream end of bottom wall spect thereto. Ahydraulic or electrically operable ram device 70, or other suitablemechanism, is employed to move the upper end of first slit-definingmember 6810 the desired predetermined location. A number of such ramsare distributed span-wise along member 68 so that the local span-wiseposition ofmember 68 may be precisely controled.

- an entraining fluid flow path 74 is defined by the first into aplurality of substantially equi-dimensioned chambers 30. Sandwichedbetween adjacent divider panels 28 and between the endmost panels andside and second slit-defining members 68 and 72 and side plates 76 and78 (FIG. 4) which extend upwardly from support frame 64 and are attachedto side walls 18 and 20 in any desired fluid-tight manner. A pressuregauge 80 is preferably attached to second slit-defining memher 72 sothat the pressure of the fluid flowing through entraining fluid flowpath 74 may bemonitored. The upper end of second slit-defining member 72has formed thereon a convexly-curved fluid-flow attachment surface orfoil 82. Fluid-flow attachment surface 82 leads from a slit 84 formedbetween the upper end of first slit-defining member 68 and the secondslitdefining member 72. The curved fluid-flow attachment surface 82 isin the form of an extended lip which recedes from the flow axis of fluidas it emerges from the slit to provide a flow attachment surface for thefluid so that it operates in accordance with the aforementioned Coandaeffect.

Leading to the entraining fluidflow path 74 through apertures providedin support frame 64 are a plurality of entraining fluid conduits 86. Theother ends of the conduits are connected to a manifold 88. The interiorof manifold 88 is connected to a suitable source of pressurizedentraining fluid through valve 90. The manifold and plurality ofconduits operate to introduce entraining fluid into entrainingfluid-flow path 74 in a uniform manner across the width of thefluid-flow path.

Cooperating with second slit-defining member 72 to form an exit aperturefrom the interior of apparatus is an articulated upper lip comprised ofa first lip element 92 pivotally attached to pin 25 so that it overhangsslit 84 and a second lip element 94 pivotally atto one another andrelative to thecurved fluidflow attachment surface 82 controls suchcharacteristics as entrainment ratios, angle of the discharged jet,turbulence and jet stability.

Curved surfaces 22, 24 and 34 and the divider panels 28 serve to smoothout the flow of the slurry as it progresses through apparatus lift. inaddition, such elements discourage coagulation, eliminate back flow,eddies and vortices, which will cause air entrainment. Also, flow path10% is designed to develop a uniform flow velocity for the slurry as itapproaches the vicinity of slit 84.

tached to lip element 92 at the outermost extent 7 thereof. Lip elements92 and 94 are adapted for relative rotation with respect to wall 14 andwith respect to each other by means of prime movers, which, in thepresent embodiment, are in the form of hydraulic rams 96a and 96b.

The operation of the aforedescribedembodiment of the present inventionis as follows: For purposes of H lustration, the apparatus and methodaccording to the present invention will be described as being utilizedin the papermaking art, with the fiber slurry being a conventional pulpslurry and the entraining fluid being water. It will be appreciated,however, that the apparatus and method may be utilized to advantage witha wide variety of slurry and entraining fluid materials.

Valve 90, controling the entraining fluid, which, in i this case, isclear or white water, is opened allowing the water to enter intomanifold 88. The water moves along entraining fluidflow path 74 andthence'through the slit 84 at which point it attaches itself to curvedfluid-flow attachment surface 82 by virtue of the Coanda effect andflows in the direction of the arrow towardthe exit aperture of apparatus10 formed between the fluid-flow attachment surface $2 and elements 92and 94.

At the same time, the desired. pulp slurry head is established inreservoir or head control box'50, and

The combined flows progress from'the region of the slit to the exitaperture and then on to the forming surface of the web former, which inthis case is Fourdrinier wire 5%. Thorough mixing of the water and pulpslurry occurs in the region between slit 84 and the exit aperture.Adjustment of lip elements 92 and 94 with respect The velocity ratio ofthe entraining fluid to the entrained slurry is one way to define theconditions for proper operation of the present apparatus. F or efficientoperation of the apparatus, the velocity ratio between the entrainingfluid and the slurry immediately upstream from the slit 84shouldpreferably be at least equal to the value of ten and, typically,may have a value of twenty or more. The high velocity differentialsexisting between these two streams result in another important advantagefor this system. The extreme shears generated will disperse the fiberflocs or agglomerates, and the simultaneous dilution by the entrainingfluid will prevent flocs from reforming. Dispersion is thus effectedfluid-dynamically eliminating the need of troublesome mechanical devicessuch as the rectifier roll.

Another way of defining the'operating conditions for this method andapparatus is to note the ratio of the kinetic energy level of theentraining fluid to that of the entrained slurry stream immediatelyupstream from the slit. Kinetic energy content at the given point ofinterest is defined as mass flow rate times velocity squared divided bytwo times g (the conversion factor) mv /2g Units derived from thisexpression are footpounds/seconds. The ratios for efficient operation ofthe apparatus and method according to this invention are preferablygreater than 5% and may run as high as 400, or more.

Operation of the structure thus far described can best be understood byreferring to F lGS. l and 2 in connection with the followingdescription. A device, as illustrated in FIGS. l and 2, was constructedhaving a width of twelveinches. Apparatus Ml wasleft open to the air anda stock head of only eleven inches, i.e., approxi mately 0.4 psi, wasmaintained. The slurry utilized was a pulp slurry and the entrainingfluid was clear or white water. During operation of this unit, the widthof slitd tl was selectively varied between 0.01 inch and 0.07 inch. Withthe velocity ratio between the entraining fluid and the slurryimmediately upstream from the slit (approximately one inch from the slitin the illustrative device) being maintained at a value of 10 or more,approximately 90 percent or more of the energy neededto accelerate thefiber slurry was supplied by the entraining fluid. Since the entrainingfluid itself contained no fibers, it was able to pass through smallvalves, small diameter tubes and orifices without plugging or shedding,

I problems which typically attend flow of a fiber slurry between thesetwo streams resulted in extreme shears through such apparatus. in thisway, the energy required to drive the system was thoroughly controledbefore it performed the ultimate. task of accelerating the fiber slurry.The high velocity differentials existing which dispersed the fiber flocsor agglomerates.

In general, it has been found that discharge velocity of the materialfrom the apparatus desscribed varies in accordaznce with changes made inthe width of the slit and the pressure of the entraining fluid, thehigher the pressure and/or the wider the slit, the higher the dischargevelocity. Likewise, the exit aperture or slice dimension A and thethroat dimension B, shown in FIG. 2, are important variables forregulating the discharge velocity of the jet. In general, minimizingthroat and slice will yield higher discharge velocites.

An important interrelationshp having a bearing on proper operation ofapparatus constructed in accordance with the teachings of the presentinvention exists between R, the radius of curvature of the fluid-flowattachment surface at the location of the slit 84, and the width(hereinafter,S) of the slit. Experimental data suggests that theapparatus will operate efficiently when the ratio of R to S, i.e., R/S,lies in the range of from 2.5 to 150.

The entrainment ratio, which is defined as the mass or volumetric ratioof the slurry stock to the entraining fluid flow, depends upon the widthof the slit and, also, upon the width of the exit aperture. Furthermore,the ratio between exit aperture or slice dimension A and the throatdimension B has a critical effect on entrainment ratios. In general, theslice-to-throat ratio increases, the entrainment ratio also increases;however, when slice-to-throat ratio exceeds unity, the resultingdivergence of the jet may limit the practical value of slice-to-throatratios greater than one. Entrainment ratio also depends on pressure ofthe entraining fluid to a lesser degree, with the entrainment ratioincreasing gradually as the pressure decreases. I

It is felt that the ability to handle a wide range-of pulpconsistencies, especially those of a high consistency, is one of theimportant advantage of the present invention as compared to the priorart. Experimentation has shown that apparatus constructed in accordancewith the teachings of the present invention is capable of handling pulpslurries in the high consistency range of from 1 to 4 percent or above,as well as those slurries in the low consistency pulp range of between0.2 and 1.0 percent. Virtually any slurry which can be delivered totheapparatus may successfully be delivered from its exit aperture athigh speeds. It should be understood that the dilution of the entrainedfiber slurry by the entraining stream is one of the necessary aspects ofoperation for the apparatus. For example, if the entrained slurry issupplied at 4 percent consistency and the entrained slurry flows in arate twice that of the entraining fluid (i.e. entrainment ratio equals2), then the discharge consistency will have been diluted to 2.67percent. Corresponding dilution of the incoming fiber will occuraccording to the entrainment ratio resulting from specific operatingconditions.

shapes of the slurry-flowpath defining means may be varied, as, forexample, in the manner illustrated in' FIG. 5. In that figure, theCoanda effect is actually utilized in a plurality of locations in theillustrated apparatus. In this embodiment, two or more fiber slurriesmay be mixed just prior to their ejection on to an appropriateweb-forming surface. In unitary chamber H0 of the illustratedalternative embodiment, for example, may be disposed a synthetic fiberslurry H2 which is kept continually mixed by means of a mixed impellerH4 driven by a suitable prime mover such as electric motor I 16. Flowingthrough conduits U8 into a flow path defined by curved baffle members120 and 122 is a second type of slurry, for example, a conventional woodpulp slurry. Alternatively, one of conduits 118 may be a source of achemical or, for that matter, plain water. Simultaneously, any desiredfluid such as water may be introduced through conduit 124 into aflowpath defined by bent wall 126 of chamber 110 and a plate 128extending downwardly from a convexly-curved fluidflow attachment surface130 formed on baffle member 122. Since a'slit is formed between theuppermost extent of bent wall 126 and the plate I28 at the locationwhere the plate joins baffle 122, the Coanda effect will operate todirect flow of the fluid passing through conduit 124 aboutconvexly-curved fluid-flow attachment surface 130. This fluid flow willserve to entrain and induceflow of synthetic fiber slurry 112 as shownby the arrows.

A convexly-curved fluid-flow attachment surface 132 is also formed onbaffle member 120 in the vicinity of a slit 134 formed by the outermostextremity of baffle member 122 and baffle member 126. This arrangementagain utilizes the Coanda effect to induce additional flow of syntheticfiber slurry I 12 and cause same to mix with the material exiting fromconduits 118.

The final application of the Coanda effect in the FIG. 5 embodiment isat the downstream end of the apparatus wherein a fluid such as water isinjected through manifold 136 and conduits 1138 into passageway M0. Thefluid exits from the passageway through a slit in the vicinity of aconvexly curved surface formed on a lower rotatable jaw member 142 whichdefines, along with upper jaw member 143, the exit aperture from theapparatus. The material, such as water, which flows through passagewayH40 attaches itself to the curved surface of the lower jaw member andthus entrains and mixes with the material flowing into engagementtherewith, the purpose of the final slit being to accelerate theincoming mixture to the final desired velocity.

The arrangement illustrated in FIG. 5 has great versatility in that itcan be used to form a wide variety of webs through the admixture ofvarious types of slurries and fluids. For example, soluble chemicals,such as wet strength aids, drainage aids or flocking agents, which mayhamper operation of upstream screens or media. equipment, mightsuccessfully be introduced in one of the entraining mecia. Chemicalreactants f one introduced on the fibers (such as polyvinyl alcohol) andthe other introduced as a soluble salt in the entraining stream (such asborax) might be utilized in the manufacture of paper products.Similarly, dispersions of foamed fibers for functional webs can beintroduced to the system and accelerated to high speeds. If desired, areinforcing scrim of nylon or other suitable material may be fed intothe system, as shown schematically and identified by means of referencenumeral 146. Because the system utilizes induced flow and a highvelocity anism, the scrim may be placed on a freely rotating roll andwill be self-fed therefrom by virtue of its entrainment in theflow pathstream. The slurry fibers will adhere to the scrim upon its exit fromthe apparatus and reinforcement means is thus provided for the finishedweb.

Referring now to FIG. 6,'still another alternative embodiment ofapparatus constructed according to the teachings of the presentinvention is illustrated. A'fiow path for the slurry being deliveredfrom a suitable reservoir is defined by curved walls 150 and 152. Thewalls converge and gradually flatten out with the terminal portionsthereof cooperating with jaw members 154 and 156, respectively, toprovide narrow slits l58'and 160, as shown. Jaw members 154 and 156 areprovided with convexly-curved fluid-flow attachment surfaces 162 and 166leading in a downstream direction from slits 158 and 160, respectively.The size of slits 158 and 160 may be varied by the operator through themanipulation of cantilever members 166 and 168 as by means of hydraulicram members 170 and 172. Fluid flow paths are defined by the jaw membersand the cantilever members so that a desired fluid may be introducedthrough the slits into the slurry flow path, as indicated by the arrows,so that the slurry is entrained at both the top and bottom thereof priorto its exit from the aperture formed by the jaw members. In other words,entraining fluidsare introduced at two locations in the system and theCoanda effect is utilized at both locations. Introduction of entrainingfluid at both locations enhances the jet discharge velocity through theexit aperture as compared to the single slit apparatus of FIGS.

1-4. The same type of entraining fluid may be used at both locations or,alternatively, two different types of while the other may be a source ofclear water. The ap paratus shown in FIG. 6 may be used, if desired, to

form a multilayered web.- To produce a two-layered web, two slurries I51and 153 are introduced thereinto from two separate sources of slurry(not shown). A thin, flexible plastic or metal strip 149, anchored at alocation upstream of entry points for slurries 151 and 153, and fixedlysecured to the side walls of the unit, maintains separation between thetwo entrained slurry streams I51 and 153, as they flow simultaneouslytoward the exit aperture. One potential application for such anarrangement may, for example, be in the manti facture of linerboardhaving a good print surface on its exterior and an inexpensive fibrousbody. This construction could be made by introducing board stock asslurry I53 and the print-grade fiber as slurry 1511. Other potentialapplications will become-readily apparent to those skilled in the art ofsheet-and web-forming. If desired, the separation strip may beadjustablymounted in any suitable mannerrelative-to the side walls of the unit sothat the relative thicknesses of the slurry layers may be selectivelyvaried.

Still another alternative embodiment of apparatus constructed inaccordancewith the teachings of the present invention is shown in FIGS.7, 8 and 9 of the drawing. This embodiment incorporates features whichrender it particularly effective for use with a wide variety of slurrymaterials and other changing operating conditions.

Large scale turbulence is an undesirable property of the jet dischargedfrom the apparatus as it leads to nonuniformities in the finished wetweb product. Through the utilization of the form of apparatus shown inFIGS. '7, 8 and 9, reduction in the scale of turbulence and consequentminimization of local irregular flow pat terns in the discharge streammay readily be effected. It has been found that the location of the slitthrough which the entraining fluid exits into the main flow path of theapparatus relative to its associated flow attachment surface has amarked influence on the formation and location of eddies, back flowsystems and vortices in the area of mixing of the entraining fluid andthe entrained slurry. This area is located between the slit and the exitaperture. The eddies and vortices which form in this mixing zone, inturn, control discharge jet stability and turbulence level. With theform of apparatus shown in FIGS. '7, 8 and 9, the location of the slitrelative to the flow attachment or foil surface may be adjusted inaccordance with changed materials or conditions encountered, such aschanges in entraining fluid or. slurry consistency or pressure, changesin the dimension of the exit'aperture, throat opening and slit width,contour and length of lips, etc. Additional influence on turbulence andefficiency of the discharge jet from the apparatus may be effectedthrough the utilization of lips of various lengths, contour andflexibility.

In the form of apparatus shown in FIGS. '7, h and 9,

two lips 174i and 1176 are employed to define at the extremities thereofan exit aperture or slice A and a throat opening B. Upper lip I74 isconnected at the up a span-wise beam element 192. The outer or down-.

stream terminal end of lower lip ll76 also cooperates with a similarbeam element 196. The clearance between lips IM and 176 (which in turninfluences discharge jet turbulence and stability) can be adjustedoverall and/or locally by appropriate motion of rams 1M and T89, anumber of which are disposed lengthwise in operative association withtheir respective beam elements 182 and 186. It is also by virtue ofadjustment .of rams 1184- and M9 and attached beam elements 162 and1196, that the thickness and velocity of the dis- 'convexly-curvedfluid-flow attachment or foil surface 266 formed on member 193. Mountedin any suitable manner for rotatable ,rnovemen't relative to member1193, is a rotatable member 196 which may be selectively positionedrelative to member 193 through the action of a cooperating geareddriving pinion T94,

which, in turn, is driven by a suitable prime mover (not shown).

Rotatable member 190 has formed therein a fluid flow path 196 forentraining fluid which is introduced therein through conduit 198. Theupper right-hand side of the flow path 196 is, as may be clearly seenwith reference to the figures, defined by a cantilever member 200 whichis fixedly attached at the lower end thereof to rotatable member 190.Attached to the upper terminal end of cantilever member 200 is aflexible, fluidflow-path defining plate 202 which has the other endthereof rigidly secured to a fixed fluid-flow-path defining member 204.Thecantilever member 200 cooperates with the curved fluid-flowattachment surface 206 formed on fixed member 193 to form a narrow slit208 through which the entraining fluid exits. A cam member 210 ismounted on a bracket affixed to rotatable member 190 to selectively varythe size of the slit 208, as desired, by its interaction with cantilever200.

Through the rotation of members 190 and 200 relative'to member 193 bypinion 194, the location of the slit 208 relative lto flow attachmentsurface 206 may be selectively varied to control turbulence andefficiency of the apparatus for a wide range of conditions, includingchanges in the entrained slurry consistency, speed of discharge jet,slice opening, basis weight of desired product. For optimum operation ofthe induced flow system according to this invention, a balance isestablished among entrainment efficiency, discharge velocity andturbulence of the discharge jet. To compensate for changes in the widthof slit 208, the height of the exit aperture A, throat opening B, andpressure of the entraining fluid, angular orientation of the slit may bechanged by rotating rotatable member 190 as shown in FIGS. 8 and 9,which illustrate the extreme positions which may be assumed by thismember. It should be noted that rotation of member 190 also has theeffect of changing the angular disposition of the-slit discharge axisrelative to the axis of the flow path. To illustrate the operation ofthe embodiment FIGS. 7, 8 and 9 more clearly, it will be assumed thatthe slurry mixture is a pulp slurry and the entraining fluid is water.After introduction of water under pressure through conduit 198, the flowis through fluid flow path 196 and then outwardly through slit 208. Thesize of the slit may be adjusted by rotation of the cam member 210against the cantilever member 200. As has been described with rspect'tothe otherembodiments of this invention, the entraining fluid issuingfrom the slit accelerates the entrained slurry stream which isintroduced into the channel formed by curved plate 178 and flexibleplate 202 from whence it progresses through lips 1'74 and 176 anddischarges onto a webety of physical characteristics. For example,either or both of the lips may be rigid or flexible. Also, the lips. maybe curved or straight, have varying lengths, or be constructed ofdifferent, suitable materials. For example, in FIGS. 7, 8 and 9, lip 174is illustrated as being straight and constructed of relatively thin,flexible plastic material while lower lip 176 is illustrated as beingcurved and constructed of stainless steel which is thick enough toprevent deformation of lip 176. Lip 174, on the other hand, is flexibleenough to deform under the pressures exerted by the slurry flow. It hasbeen found that at least under certain conditions the use of at leastone flexible lip results in minimizing turbulence and increasingentrainment efficiency due to the ability of the flexible lip to respondto changes in pressures exerted thereon by the slurry flow. If desired,the lips may be selectively releasably secured to the rest of theapparatus by means of clamps or other releasable attachment means sothat different types of lips may be interchanged, as desired by theoperator.

Although the apparatus according to the present invention has thus farbeen illustrated as being utilized to deliver slurry streams in agenerally horizontal direction onto a horizontally disposed web-formingsurface, the principles of the invention may be employed on apparatusadapted to deliver a slurry in other than a horizontal direction andonto a web-forming surface that is disposed other than horizontally; forexample, the present system may be utilized in combination with agenerally vertically disposed twin wire paper former, such as theVerti-Former former manufactured by the Black Clawson Company and theBel Baie former manufactured by Beloit Corporation.

An embodiment of the present invention that may be employed inconnection with generally vertically disposed forrners is illustrated inFIG. 10. This apparatus incorporates several features already discussed,such as the dual entraining fluid system and dual fluid attachmeritsurfaces which permit operation at speeds-and slice openings greaterthan those obtainable with the single foil surface arrangement. Also,the apparatus of FIG. 10 incorporates an arrangement whereby the posi- 1tion or discharge angle of the entraining fluid slits may be varied withrespect to the direction of slice discharge, thus providing a highdegree of adjustability to the system. Furthermore, the system can befed with two or more separate entrained flow slurries or with a singleslurry, as desired.

The entraining flow is supplied under pressure through flexible supplyconduits 198a and 19812 and attaches to the fluid-flow attachmentsurfaces 206a and 206!) formed on members 103a and 193i).

The slit openings can be adjusted by operating cams 210a and 210b, whileslit location with respect to the fluid-flow attachment surfaces 206aand 206b can be appropriately adjusted by rotation of pinions 194a and1194b which, in turn, will rotate members a and b and other integrallyattached elements in the manner previously disclosed relative to theapparatus lid of FIGS. ,7, 8 and 9. Dimension B, which is the throat ordistance between the foil surfaces 206a and 206b, is not adjustable inthe arrangement here illustrated; however, suitable means for providingsuch adjustment could be readily devised and utilized where appropriate.

The entrained slurry is supplied from one or more head control boxessimilar in design and concept to that shown in FIG. 1, but notillustrated in FIG. 10. Slurry flow from the head control box (or boxes)then proceeds via flexible tubes 212a and 2ll2b through side walls 214aand 2141b into a passageway defined by lower baffle member 220 andcurved upper plates 222a and 2221) which are attached to the side walls.The walls 214a and 214b, the plates 222a and 222b and the lower bafflemember 220 may be constructed of any suitable material, such as plasticor stainless steel.

Plates 222a and 22% are curved upwardly, as shown, to provide acentrally disposed orifice in communication with'throat opening B. Theuppermost portions of the plates 222a and 22212 are in fluid-tight,slideable engagement with cantilever members 200a and 200b,respectively. Member 220 is shaped to insure that the slurry passagewaygradually converges as it approaches the throat opening. Two ormore-types of slurry material may be introduced into the system merelyby placing conduits 212a and 21212 in communication with separatesources of different slurries. Slurry material will then enter thesystem from both the right and left sides, as viewed in FIG. 10. If,however, the operator wishes to draw slurry from only one side of theunit, a baffle plate, such as baffle plate 240 (illustrated by dashedlines), may be mounted in any suitable manner within the system to cutoff flow from one side or other of the system.

By virtue of the Coanda effect previously described, slurry flowing intothe passage defined by plates 222a, 222b and baffle member 220 is drawninto the throat opening and through the passage formed by the slice lips176a and T7619 which are suitably positioned by prime movers 186a and18617. The combined flows then proceed toward the exit aperture wherethe discharge is intercepted between the converging continuous twinwires 216a and 216b which, together, comprise the web former section ofa generally vertically disposed twin wire former of the type describedabove. For purposes of simplicity, only this portion of the former isshown since the operation of such devices is well knovim.

We claim:

1. Apparatus for delivering a fiber slurry to the forming surface ofasheetor web-forming machine, includmeans defining a flow path forsaidslurry and leading to an elongate exit aperture; means defining atleast one elongate,

communicating with said flow path and-extending narrow slit lidsubstantially parallel to said exit aperture closely adjacent thereto;

means for introducing an entraining fluid through said slit and intosaid flow path at a velocity substantially greater than the flowvelocity of said slurry immediately upstream from said slit; and

a convex, generally curved fluid-flow attachment surface leading fromsaid slit toward said exit aperture to which the entraining fluidattaches itself due to the Coanda effect and exerts a substantialpulling force on said slurry to entrain and accelerate said slurrytoward said exit aperture while mixing with said slurry, and provide ahigh percentage of all energy required to accelerate said slurry.

2. The apparatus according to claim ll wherein said slit is disposedsubstantially perpendicularly to said 3. The apparatus according toclaim ll including means for selectively varying the location of saidslit relative to said flow attachment surface.

4. The apparatus according to claim ll including means for selectivelyvarying the angular disposition of said slit relative to said slurryflow path.

5. The apparatus according to claim ll wherein said flow-path definingmeans includes a pair of spacedapart lips for directing said entrainingfluid and the en trained slurry to said forming surface.

6. The apparatus according to claim 5 wherein said fluid-flow attachmentsurface is formed on at least one of said lips.

7. The apparatus according to claim 5 additionally including means foradjustably moving said lips relative to one another.

8. The apparatus according to claim 5 wherein at least oneof said lipsis constructed of a flexible material.

9. The apparatus according to claim 5 wherein one of said lips extendsinwardly from said exit aperture a sufficient distance such that aportion thereof is juxtaposed relative to said slit.

10. The apparatus according to claim ll wherein said entraining fluidintroduction means is adapted to introduce said entraining fluid intosaid flow path at a flow velocity equal to at least ten times the flowvelocity of the slurry immediately upstream from said slit.

111. The apparatus according to claim E wherein said entraining fluidintroduction means is adapted to introduce said entraining fluid intosaid flow path at a kinetic energy level of at least fifty times themagnitude of the kinetic energy level of the slurry immediately uptached thereto in a downstream direction.

M. The apparatus according to claim 13 additionally including separatormeans disposed in said flow path between at least some of saidfluid-flow attachment surfaces.

15. The apparatus according to claim 1 wherein said means defining aflow path for said slurry includes a headbox chamber.

16. The apparatus according to claim wherein baffle means is disposed insaid headbox chamber for the purpose of smoothing the flow of saidslurry along said flow path.

'17. The apparatus according to claim 1 wherein the ratio of the radiusof curvature of said surface at the slit location to the width of saidslit in the range from 2.5 to 150.

18. A method for delivering a fiber slurry to the forming surface of asheetor web-forming machine, comprising the steps of:

introducing a slurry mixture into a predetermined injecting a fluidunder pressure through an elongated slit disposed substantiallyperpendicular to said flow path into said flow path at a predeterminedlocation upstream of said forming surface and at a velocitysubstantially greater than the velocity of the slurry mixtureimmediately upstream from said location; attaching the injected fluiddue to the Coanda effect to a convex, generally curved fluid-flowattachmentsurface leading in a downstream direction from saidpredetermined injection location whereby the injected fluid exerts asubstantial pulling force on said slurry and entrains and acceleratesthe flow of the slurry along said predetermined flow path, and providesa high percentage of all energy required to accelerate said slurry;mixing the injected fluid and the slurry; and directing the mixed fluidand entrained slurry onto the forming surface. 19.The method accordingto claim 18 wherein the step of entraining said slurry is accomplishedby creating a zone of reduced pressure in said flow path in the vicinityof said fluid-flow attachment surface.

20. The method according to claim 18 wherein said injected fluid iswater.

21. The method according to claim 18 wherein said fluid is injected intosaid predetermined flow path at a flow velocity equal to at least tentimes the flow velocity of the slurry immediately upstream of saidpredetermined location.

22. The method according to claim 18 wherein said fluid is injected intosaid predetermined flow path at a kinetic energy level ofat least fiftytimes the magnitude of the kinetic energy level of the slurryimmediately. upstream from said slit. 23. A method for delivering aslurry to the forming surface of a sheetor web-forming machine,comprising the steps of:

introducing a slurry mixture into a predetermined flow path leadingtoward an exit aperture disposed adjacent to said forming surface;introducing an entraining fluid into said flow path under pressure inthe form of a thin, elongated stream; and directing the flow of saidfluid toward said exit aperture by attaching said thin, elongated streamof fluid due to the Coanda effect toa convex, generally curvedfluid-flow attachment surface leading from the location of introductionof said slurry toward said exit aperture whereby said slurry is pulledtoward said exit aperture by a substantial pulling force exerted by saidfluid to provide a high percentage of all energy required to acceleratesaid slurry. 24. In combination: means defining a forming surface; andmeans for delivering a slurry to said forming surface comprising: a.means defining a predetermined flow path for said slurry leading to anelongate exit aperture through which said slurry is adapted to dischargeinto engagement with said forming surface; b. means defining at leastone elongate restricted opening communicating with said flow pathclosely adjacent to said exit aperture and in substantially parallelrelationship thereto;

c. a convex, generally curved fluid-flow attachment surface leading fromsaid restricted opening toward said exit aperture; and

d. means for introducingan entraining fluid under pressure into saidflow path through said restricted opening whereby said fluid attachesitself to said fluid-flow attachment surface due to the Coanda effect toexert a substantial pulling force on said slurry and direct said slurrytoward said exit aperture and provide a high percentage of all energyrequired to accelerate said slurry.

*aaaa Dated December 10,, 197

Patent No.

Inventofls) Sangho E. Back et a1 It is certified that error appears inthe above-identified patent and that said Letters Patent are herebycorrected as shown below:

On the Title Page, the following; should be added:

--- [75} Assignees: Cromi Zellerbech Corporation, San

Francisco Calif Signed and sealed this 15th day of July 1.975.,

(SEAL) Attest 5 Ce MARSHALL DANN RUTH C, MASON Commissioner of PatentsArresting Officer and Trademarks USCOMM'DC 60376-P69 u.s. GOVIRNMENTPmmme OFFICE: 8 930

1. Apparatus for delivering a fiber slurry to the forming surface of asheet- or web-forming machine, including: means defining a flow path forsaid slurry and leading to an elongate exit aperture; means defining atleast one elongate, narrow slit communicating with said flow path andextending substantially parallel to said exit aperture closely adjacentthereto; means for introducing an entraining fluid through said slit andinto said flow path at a velocity substantially greater than the flowvelocity of said slurry immediately upstream from said slit; and aconvex, generally curved fluid-flow attachment surface leading from saidslit toward said exit aperture to which the entraining fluid attachesiTself due to the Coanda effect and exerts a substantial pulling forceon said slurry to entrain and accelerate said slurry toward said exitaperture while mixing with said slurry, and provide a high percentage ofall energy required to accelerate said slurry.
 2. The apparatusaccording to claim 1 wherein said slit is disposed substantiallyperpendicularly to said slurry flow path.
 3. The apparatus according toclaim 1 including means for selectively varying the location of saidslit relative to said flow attachment surface.
 4. The apparatusaccording to claim 1 including means for selectively varying the angulardisposition of said slit relative to said slurry flow path.
 5. Theapparatus according to claim 1 wherein said flow-path defining meansincludes a pair of spaced-apart lips for directing said entraining fluidand the entrained slurry to said forming surface.
 6. The apparatusaccording to claim 5 wherein said fluid-flow attachment surface isformed on at least one of said lips.
 7. The apparatus according to claim5 additionally including means for adjustably moving said lips relativeto one another.
 8. The apparatus according to claim 5 wherein at leastone of said lips is constructed of a flexible material.
 9. The apparatusaccording to claim 5 wherein one of said lips extends inwardly from saidexit aperture a sufficient distance such that a portion thereof isjuxtaposed relative to said slit.
 10. The apparatus according to claim 1wherein said entraining fluid introduction means is adapted to introducesaid entraining fluid into said flow path at a flow velocity equal to atleast ten times the flow velocity of the slurry immediately upstreamfrom said slit.
 11. The apparatus according to claim 1 wherein saidentraining fluid introduction means is adapted to introduce saidentraining fluid into said flow path at a kinetic energy level of atleast fifty times the magnitude of the kinetic energy level of theslurry immediately upstream from said slit.
 12. The apparatus accordingto claim 1 additionally including means for adjusting the size of saidslit.
 13. The apparatus according to claim 1 wherein a plurality ofslits communicate with said flow path and said means for introducingsaid entraining fluid into said flow path includes means for forcingentraining fluid through each slit and a fluid-flow attachment surfaceleading from each slit, each said fluid-flow attachment surface beingpositioned to direct the fluid attached thereto in a downstreamdirection.
 14. The apparatus according to claim 13 additionallyincluding separator means disposed in said flow path between at leastsome of said fluid-flow attachment surfaces.
 15. The apparatus accordingto claim 1 wherein said means defining a flow path for said slurryincludes a headbox chamber.
 16. The apparatus according to claim 15wherein baffle means is disposed in said headbox chamber for the purposeof smoothing the flow of said slurry along said flow path.
 17. Theapparatus according to claim 1 wherein the ratio of the radius ofcurvature of said surface at the slit location to the width of said slitin the range from 2.5 to
 150. 18. A method for delivering a fiber slurryto the forming surface of a sheet- or web-forming machine, comprisingthe steps of: introducing a slurry mixture into a predetermined flowpath; injecting a fluid under pressure through an elongated slitdisposed substantially perpendicular to said flow path into said flowpath at a predetermined location upstream of said forming surface and ata velocity substantially greater than the velocity of the slurry mixtureimmediately upstream from said location; attaching the injected fluiddue to the Coanda effect to a convex, generally curved fluid-flowattachment surface leading in a downstream direction from saidpredetermined injection location whereby the injected fluid exerts asubstantial pulling force on said slurry and entrains and acceleratestHe flow of the slurry along said predetermined flow path, and providesa high percentage of all energy required to accelerate said slurry;mixing the injected fluid and the slurry; and directing the mixed fluidand entrained slurry onto the forming surface.
 19. The method accordingto claim 18 wherein the step of entraining said slurry is accomplishedby creating a zone of reduced pressure in said flow path in the vicinityof said fluid-flow attachment surface.
 20. The method according to claim18 wherein said injected fluid is water.
 21. The method according toclaim 18 wherein said fluid is injected into said predetermined flowpath at a flow velocity equal to at least ten times the flow velocity ofthe slurry immediately upstream of said predetermined location.
 22. Themethod according to claim 18 wherein said fluid is injected into saidpredetermined flow path at a kinetic energy level of at least fiftytimes the magnitude of the kinetic energy level of the slurryimmediately upstream from said slit.
 24. In combination: means defininga forming surface; and means for delivering a slurry to said formingsurface comprising: a. means defining a predetermined flow path for saidslurry leading to an elongate exit aperture through which said slurry isadapted to discharge into engagement with said forming surface; b. meansdefining at least one elongate restricted opening communicating withsaid flow path closely adjacent to said exit aperture and insubstantially parallel relationship thereto; c. a convex, generallycurved fluid-flow attachment surface leading from said restrictedopening toward said exit aperture; and d. means for introducing anentraining fluid under pressure into said flow path through saidrestricted opening whereby said fluid attaches itself to said fluid-flowattachment surface due to the Coanda effect to exert a substantialpulling force on said slurry and direct said slurry toward said exitaperture and provide a high percentage of all energy required toaccelerate said slurry.
 32. A METHOD FOR DELIVERING A SLURRY TO THEFORMING SURFACE OF A SHEET- OR WEB-FORMING MACHINE, COMPRISING THE STEPSOF: INTRODUCTING A SLURRY MIXTURE INTO A PREDETERMINED FLOW PATH LEADINGTOWARD EXIT APERTURE DISPOSED ADJACENT TO SAID FORMING SURFACE;INTRODUCING AN ENTRAINING FLUID INTO SAID FLOW PATH UNDER PRESSURE INTHE FORM OF A THIN, ELONGATED STREAM; AND DURECTING THE FLOW OF SAIDFLUID TOWARD SAID EXIT APERTURE BY ATTACHING SAID THIN, ELONGATED STREAMOF FLUID DUE TO THE COANDA EFFECT TO A CONVEX, GENERALLY CURVEDFLUID-FLOW ATTACHMENT SURFACE LEADING FROM THE LOCATION OF INTRODUCTIONOF SAID SLURRY TOWARD SAID EXIT APERTURE WHEREBY SAID SLURRY IS PULLEDTOWARD SAID EXIT APERTURE BY A SUBSTANTIAL PULLING FORCE EXERTED BY SAIDFLUID TO RPOVIDE A HIGH PERCENTAGE OF ALL ENERGY REQUIRED TO ACCELERATESAID SLURRY.